Desired hardness and strength properties of metals, particularly ferrous metals and especially metal alloys such as carbon steel and alloy steel, are secured by heat treatment of the metal object. The properties usually depend upon establishment of certain physical structures in the metal. The production of the desired physical structures is obtained by heating the metal to a temperature where the structure is present, then by arresting at the desired point the changes in the internal structure which take place during cooling of the metal from high temperatures. Quick cooling by quenching the heated object in a quenching medium makes it possible to arrest the physical changes at the desired point during cooling.
Quenching in the quenching medium is carried out in such a manner that the physical changes in the metal are arrested at the desired point, usually at the point at which maximum hardness is obtained. Subsequently, the heat treated and quenched object may be subjected to treatment at lower temperature (annealing or tempering) to provide the desired degree of toughness and ductility.
For many years mineral oil based quenching fluids have been used. Previously, aqueous quenching media were employed. The aqueous fluids provided extremely rapid cooling setting up excessive amounts of internal stress in the object. Mineral oil based fluids avoided this difficulty, but often did not provide a sufficiently high cooling rate to secure desirable properties in pieces formed of materials having high critical cooling rates to develop maximum strength and hardness or to quench pieces of high mass to surface ratios to develop hardness and strength to maximum depth.
It is also desirable to provide quench oils that possess sufficient durability, cleanliness and consistency. Durability refers to additive lifetime after being exposed to thermal stressing while consistency relates to constant additive performance over time. Cleanliness relates to amounts of deposits on the workpiece and/or staining thereof and is measured using a coker test.
A detailed description of heat treating of steel appears at pages 961 et seq of the Metals Handbook, Desk Edition, Second Edition, J. R. Davis, Ed., ASM International, Metals Park, Ohio, USA (1998). A discussion of quenching appears at pages 973-975 of that text.
U.S. Pat. No. 2,340,724 relates to quenching oils comprising a light mineral quenching oil and an oil-soluble, heat stable, high molecular weight iso-olefin polymerization product in a controlled amount adequate to produce a quenching oil composition having an initial 5-second quenching speed of at least 22.0 percent without substantially modifying the stress-reducing characteristics of the oil. Polymers of molecular weigh 1,000 to 10,000, and particularly, isobutylene polymerization product, are said to be particularly advantageous.
U.S. Pat. No. 3,489,619 relates to oil compositions described as having good high temperature stability and useful as a heat transfer oil for the quenching of metals. The oil comprises a major proportion of a hydrocarbon lubricating oil into which has been dispersed a minor proportion of an alkali metal phosphate, silicate or borate with the aid of a minor proportion of a high molecular weight mono-carboxylic acid, dicarboxylic acid or dicarboxylic acid anhydride.
U.S. Pat. No. 3,567,640 describes a quenching oil composition comprised of a major portion of a petroleum oil having a viscosity within the range of about 40 to about 300 SUS at 100° F. and a flash point in excess of 250° F. and about 2% to about 15% by weight of a quench oil additive, which is an oil soluble petroleum resin produced from distillates of cracked petroleum stock having a melting point of at least 40° C. and an aniline point value of less than 50° C.
U.S. Pat. No. 3,855,014 describes an improved quenching oil composition comprising a major amount of a quench oil of lubricating viscosity; a minor amount of at least one carbon-linked poly-phenate metal compound sufficient to improve the anti-staining properties of the composition and at least one naphthyl amine sufficient to improve the resistance to oxidation of the composition. The composition may also include a minor amount of at least one of certain diamine components said to provide further improved oxidation resistance.
U.S. Pat. No. 5,015,404 describes an oil composition containing 100 parts by weight of a base oil selected from the group consisting of mineral base oil, synthetic base oil and mixtures thereof, and 0.1 to 20 parts by weight of a hydrogenated oil obtained by hydrogenating an oil selected from the group consisting of coal type tar, oil produced by fractionating coal type tar, a hydrocarbon obtained by thermally cracking petroleum and having a boiling point of not lower than 200° C., a hydrocarbon obtained by catalytically cracking petroleum and having a boiling point of not lower than 200° C., a hydrocarbon obtained by catalytically reforming petroleum and having a boiling point of not lower than 200° C., and mixtures thereof, whereby the hydrogenated oil has the hydrogen-donating properties of not lower than three times the hydrogen-donating properties of the base oil at temperatures of not lower than 350° C.
U.S. Pat. No. 5,250,122 discloses a heat treating oil composition which comprises (A) at least one base oil selected from a mineral oil and a synthetic oil each having a sulfur content of not more than 300 ppm and (C) at least one member selected from alkaline earth metal salts of salicylic acid. There is also disclosed a heat treating oil composition which comprises (I) a base oil having a sulfur content of 3 to 1000 ppm consisting of said (A) component and (C) at lease one member selected from a sulfur and a sulfur compound, along with (II) various additives for quenching. This heat treating oil composition is said to be suitable for quenching under the condition of a high oil temperature and capable of obtaining a treated metal excellent in brightness and having a minimized distortion.
U.S. Pat. No. 5,376,186 describes a heat treating oil composition which comprises a base oil adjusted to have a total sulfur content of 3 to 1000 ppm comprising (A) at least one base oil selected from a mineral oil and a synthetic oil each having a sulfur content of not more than 300 ppm and (C) at least one member selected from a sulfur and a sulfur compound, and (B) at least one additive selected from an alkaline earth metal salt of sulfonic acid, that of a phenol, alkenyl succinic acid derivatives, fatty acid or its derivatives and phenol-based and amine-based antioxidants. The above-mentioned heat treating oil composition is said to be suitable for quenching under a condition of a high oil temperature to realize a treated metal product having a excellent brightness and little distortion.
U.S. Pat. No. 5,487,796 relates to a method of quenching metals, in particular steel alloys includes treatment of the article being quenched in a boiling aqueous solution of sodium tetraborate, with gas being additionally introduced into the quench bath. The supply of gas enables a continuous operation in a wide range of application and avoids the use of conventional less environmentally friendly quenching media (oils).
U.S. Pat. No. 5,879,743 describes a wear-resistant hardfacing and a method for applying such a hardfacing. A finely powdered, wear-resistant alloy and a polyvinyl alcohol (PVA) solution slurry is coated onto the metal surface of a tool, implement, or similar item to be hardfaced. Alternatively, a binding coating of PVA solution may be applied to the metal surface followed by application of a layer of a powdered alloy. After the slurry or PVA binding coating has dried, leaving a dry coat of alloy in a PVA matrix, the metal surface is heated to the fusion temperature of the alloy in vacuum, in an inert gas atmosphere, or in hydrogen atmosphere. The metal item with the fused coating is heat treated to impart desired mechanical properties to the part substrate material. The method of the present invention gives a smooth, dense coating of the wear-resistant hardfacing without nonmetallic inclusions.
U.S. Pat. No. 6,239,082 describes petroleum quench oils described as effective for high speed cooling of heated metals and metal hardening. The petroleum quench oils contain natural or synthetic base oils having a minimum flash point of about 120° C. and a combination of poly(iso)alkylene and poly(iso)alkylene succinic anhydride or succinic acid. A method for cooling heated metal to harden it, improve the metallurgical consistency, improve machinability and reduce residue on quenched metal parts is also disclosed comprising quenching the heated metal part in a quench oil containing natural or synthetic base oils having a minimum flash point of about 120° C. and a combination of poly(iso)alkylene and poly(iso)alkylene succinic anhydride or succinic acid.
Copending, commonly assigned patent application Docket No. 3097R is directed to a quenching oil composition comprising (1) an oil having kinematic viscosity (ASTM Test Method D-445) at 40° C. ranging from about 4 to about 45 mm2sec−1 (about 40 to about 210 Saybolt Universal Seconds (SUS)) and having a saturated content from about 80% to about 100%; (2) an aliphatic polyolefin having Mn ranging from about 300 to about 10,000; and (3) at least one member selected from members of the groups consisting of (a) a metal salt of hydrocarbyl substituted phenols, salicylic acids, carboxylic acids, and sulfonic acids; and optionally, at least one member selected from members of the groups consisting of (b) hydrocarbyl substituted succinic esters, amides, ester-amides, imides, amine salts, acid-esters, acid-amides ester-amine salts, amide-amine-salts and acid-amine salts.
The quench oils of the instant invention afford durability, consistency and suitable quenching characteristics. Suitable quenching characteristics include a high maximum cooling rate and a high maximum cooling rate temperature signifying collapse of the vapor barrier between the workpiece and the quenching oil, and a lower cooling rate (6-8° C.) after the workpiece has reached 300° C. to prevent thermal distortion/cracking.